Soap was traditionally made by mixing animal fats with lye obtained from such sources as the ashes of a wood tire. In modern times, many soaps are mixtures of sodium or potassium salts of fatty acids and are produced from oils or fats by reacting them at elevated temperatures with an alkali such as sodium or potassium hydroxide.
Vegetable oils, as such as olive oil, are produced by pressing oil-bearing seeds, usually by hydraulic power presses. For example, olive presses known in the art work by the application of pressure to olive paste to separate the liquid oil and vegetation water from the solid material. The oil and vegetation water are then separated by standard decantation.
This method is still widely used today, and it remains a valid way of producing high quality olive oil if adequate precautions are taken. First the olives are ground into an olive paste, using large grindstones. The olive paste generally stays under the stones for about half an hour, this has three objectives, namely to guarantee that the olives are well ground, to allow enough time for the olive drops to join to form the largest droplets of oil and to allow the fruit enzymes to produce some of the oil aromas and taste. Rarely, olive oil mills use a modern crushing method with a traditional press. After grinding, the olive paste is spread on fiber disks, which are stacked on top of each other, then placed into the press. Traditionally the disks were made of hemp or coconut fiber, but nowadays they are made of synthetic fibers which are easier to clean and maintain. These disks are then put on a hydraulic piston, forming a pile. Pressure is applied on the disks, thus compacting the solid phase of the olive paste and percolating the liquid phases (oil and vegetation water). The applied hydraulic pressure can go to 400 atm. To facilitate separation of the liquid phases, water is run down the sides of the disks to increase the speed of percolation. The liquids are then separated either by a standard process of decantation or by the means of a faster vertical centrifuge. The traditional method is a valid form of producing high quality olive oil, if after each extraction the disks are properly cleaned from the remains of paste; if not the leftover paste will begin to ferment thereby producing inconsistencies of flavors (called defects) that will contaminate the subsequently produced olive oil. A similar problem can affect the grindstones, that in order to assure perfect quality, also require cleaning after each usage.
Various industrial decanters are applicable in this invention. With the standard three phases oil decanter, a portion of the oil polyphenols is washed out due to the higher quantity of added water (when compared to the traditional method), producing a larger quantity of vegetation water that needs to be processed. The two phase oil decanter was created as an attempt to solve these problems. Sacrificing part of its extraction capability, it uses less added water thus reducing the phenol washing. The olive paste is separated into two phases: oil and wet pomace. This type of decanter, instead of having three exits (oil, water and solids), has only two. The water is expelled by the decanter coil together with the pomace, resulting in a wetter pomace that is much harder to process industrially. Many pomace oil extraction facilities refuse to work with these materials because the energy costs of drying the pomace for the hexane oil extraction often make the extraction process sub-economical. In practice, then, the two phase decanter solves the phenol washing problem but increases the residue management problem.
This process leaves as a residue a dense cake of crushed and compressed seed husks from which further extraction of oil would cost more than the value of the oil extracted. This dense slab is used to some extent for animal feed, but most of it is discarded as a useless agricultural effluent of no economic value.
U.S. Pat. Nos. 3,823,774 and 3,892,668 to Chiu disclose a digested alkaline tall oil pitch soap composition produced by heating tall oil pitch with excess aqueous alkali. Tall oil pitch is a byproduct of the Kraft process for making paper, and comprises fatty acids and rosin acids and their esters and approximately one-third unsaponifiable organic material. The soap is produced by mixing, for each part by weight of tall oil pitch, 1-5 parts by weight of an aqueous base solution containing 20-80% excess alkalinity, and heating the mixture of a time and temperature equivalent to from about 4 hours at 70° C. to about 16 hours at 100° C.
U.S. Pat. No. 4,483,742 to Bridle discloses liquid soaps for use in paper recycling and other industrial cleaning or scouring processes. The liquid soap comprises an aqueous partially saponified mixture comprising 1 part pine oil (a mixture of terpene alcohols and hydrocarbons) and from 1 to 20 parts of a soap-making fatty acid, such as tall oil or distilled oil. The mixture is preferably saponified by use of 30% sodium hydroxide solution. The liquid soap may contain less than 10% water.
U.S. Pat. No. 6,020,509 to Weerasooriya discloses a process for producing a surfactant composition by partially saponifying an alkoxylated triglyceride with an alkali metal hydroxide such as sodium hydroxide and recovering a surfactant composition comprising soap and moisturizing agents comprised of alkoxylated monoglycerides and un-reacted alkoxylated triglycerides.
U.S. Pat. No. 6,380,153 to Carlson discloses methods of producing surfactant compositions in which processed plant material is used to enhance the saponification process to produce surfactant compositions having enhanced surfactant, mechanical cleaning and emollient characteristics. The plant material provides additional oils and triglycerides for reaction in the saponification process and provides an improved reaction interface, thereby producing surfactant compositions of improved character.
U.S. Pat. No. 6,440,908 to Racherla discloses a high-moisture bar comprising at least 30% anhydrous soap and 20-60% water, in which a borate compound is used to structure the water and thus enable the bar to retain a high moisture content without compromising other bar properties.
Hence a soap made of organic residues from olive oil manufacture (e.g. said dense slab or cake of crushed and compressed seed husks) is still a long felt need.